In the past, nitrile rubber (acrylonitrile-butadiene copolymer rubber) has been used as a material for rubber parts for automobile such as hoses, and tubes by making use of its oil resistance, mechanical properties, chemical resistance, etc. Further, hydrogenated nitrile rubber obtained by hydrogenating the carbon-carbon double bond in the polymer main chain of the nitrile rubber (hydrogenated acrylonitrile-butadiene copolymer rubber) is further excellent in heat resistance, so it is used for rubber such as belts, hoses, and diaphragms.
In view of such a situation, Patent Document 1 discloses a hydrogenated nitrile rubber composition comprised of 100 parts by weight of hydrogenated nitrile rubber having an acrylonitrile content of 25 to 44 wt % and an iodine value of 32 to 65 or a blend of the hydrogenated nitrile rubber, 2 to 23 parts by weight of an ester-based plasticizer, and 0.5 to 10 parts by weight of an organic peroxide. According to the hydrogenated nitrile rubber composition disclosed in Patent Document 1, a cross-linked rubber excellent in fuel oil resistance and the like can be obtained, but the sour gasoline resistance is not sufficient, the tension set is also large, and sometimes the rubber is not suited for applications where a small tension set is required, for example, seal applications.